Radio-frequency identification (RFID) devices are attached to products or packaging to provide information about the products. RFID devices typically include a device substrate with an antenna and an integrated circuit disposed on the device substrate. An external RFID communication system provides an RFID signal that is received by the antenna of the RFID device. The received signal provides information and electrical power to the integrated circuit, which then responds with an electromagnetic response signal that is received by the RFID communication system. The response signal provides information about the product or package to which the RFID is attached.
Near-field-communications (NFC) systems also provide an electronic response to electromagnetic stimulation for enabling financial transactions by employing a set of electromagnetic communication protocols that enable two electronic devices, one of which is usually a portable device such as a smartphone, to communicate by bringing them within 4 cm of each other. These devices use electromagnetic induction between two loop antennae to communicate and transmit power, for example as disclosed in U.S. Pat. No. 7,688,270. Thus, at least one of the devices can operate without a stored energy device such as a battery.
Electromagnetically stimulated communication devices are typically made by printing, stamping, or laminating an antenna onto a provided communication device substrate and then affixing an integrated circuit to the provided communication device substrate. The integrated circuit is encapsulated in a plastic or ceramic package with connection pins and electrically connected to the antenna using wires formed on the device substrate using photolithographic, surface mount, or soldering methods. The integrated circuit can be a surface mount device and is disposed on the device substrate using methods such as pick-and-place. At present, the smallest device that can be disposed using conventional methods has a width or length of at least 200 microns. Thus, such communication devices are relatively large and readily visible to an observer. The communication device substrate is then affixed to a package or label that is applied to or encloses an object.
An alternative method for transferring active components from one substrate to another is described in AMOLED Displays using Transfer-Printed Integrated Circuits published in the Proceedings of the 2009 Society for Information Display International Symposium Jun. 2-5, 2009, in San Antonio Tex., US, vol. 40, Book 2, ISSN 0009-0966X, paper 63.2 p. 947. In this approach, small integrated circuits are formed over a buried oxide layer on the process side of a crystalline wafer. The small integrated circuits, or chiplets, are released from the wafer by etching the buried oxide layer formed beneath the circuits. A PDMS stamp is pressed against the wafer and the process side of the chiplets is adhered to the stamp. The chiplets are pressed against a destination substrate or backplane coated with an adhesive and thereby adhered to the destination substrate. The adhesive is subsequently cured. In another example, U.S. Pat. No. 8,722,458 entitled Optical Systems Fabricated by Printing-Based Assembly teaches transferring light-emitting, light-sensing, or light-collecting semiconductor elements from a wafer substrate to a destination substrate or backplane.
In such methods it is generally necessary to electrically connect the small integrated circuits or chiplets to electrically conductive elements such as contact pads on the destination substrate. By applying electrical signals to conductors on the destination substrate, the small integrated circuits are energized and made operational. The electrical connections between the small integrated circuits and the contact pads are typically made by photolithographic processes in which a metal is evaporated or sputtered onto the small integrated circuits and the destination substrate to form a metal layer, the metal layer is coated with a photoresist that is exposed to a circuit connection pattern, and the metal layer and photoresist are developed by etching and washing to form the patterned electrical connections between the small integrated circuits and the contact pads on the destination substrate. Additional layers, such as interlayer dielectric insulators can also be required. This process is expensive and requires a number of manufacturing steps. Moreover, the topographical structure of the small integrated circuits over the destination substrate renders the electrical connections problematic. For example, it can be difficult to form a continuous conductor from the destination substrate to the small integrated circuit because of the differences in height over the surface between the small integrated circuits and the destination substrate.
Electromagnetically stimulated communication devices are widely used in cost-sensitive applications, such as tracking, financial transactions, and anti-counterfeiting. It is desirable to make these communication devices small to reduce their costs and make them available on a wide variety of substrates, for example flexible substrates. In some applications it is useful to render the communication devices difficult to perceive by the human visual system. There is a need, therefore, for an efficient, effective, and low-cost method of manufacturing such communication devices that reduces both the size of the communication devices and their cost.